Hi Russell
Do they have screw on valve stems out your way? Last time I was buying new tubes had the same issue. Then one of the heavy truck tire outfits suggested tubes with screw on stems. They had to order the tubes and the stems but they had them in pretty short order. But they have worked fine. I don't remember the brand but it was of better known brands.
The ones in my picture are the long stems, the ones they got me were about half the length. They also had them longer.
Cheers Phil